Controller not charging

[TL2021]

I’m having an issue with charging and discharging that’s driving me nuts. I built a 24v system recently that worked well for a day. Now I’m not getting the same results.

Day 1, I was able to solar charge my battery while discharging. I hooked up my car to the inverter. I spent a few cloudy days charging my battery back up. I tried charging the battery with a plug in battery charger, but it would never go past 27.6v when the charger was hooked up. I noticed on the app that the battery would read ~29.2v when I cut the charger on (Even though it would push no current). But it would quickly go back down to 27.6 when I cut it off.
Today, I’m having the same issue with my mppt charge controller. It reads the battery as high as 33v sometimes, but usually settles around 29.2. But when I cut off the panels, it drops down to ~26v. My inverter keeps cutting off because it’s not getting enough from my battery and solar since the controller and even my charger thinks the battery is full.

What is happening?

8s 280ah
8s 200a bms
60a mppt solar charge controller
Victron Blue Smart 24v charger

 

[MisterSandals]

I hooked up my car to the inverter.

Is this connected to the battery or the SCC's load output?

Have you tested any of the volt readings with an actual digital volt meter or are these readings from the various devices displays?

My inverter keeps cutting off because it’s not getting enough from my battery and solar since the controller and even my charger thinks the battery is full.

Does the inverter cut off with an error code like low voltage or ??
Why do you suspect that the controller and charger think the battery is full?
Are you simultaneously using the MPPT SCC and the Victron 24v charger?

Sorry, there is a LOT going on in your description, just trying to figure it out.

 

[snoobler]

Is the inverter cutting off because of the 33V spike? many cut off at 32V or less.

27.6V is at a high state of charge.

Check all connections - everything is tight and secure.

Have you confirmed any readings with a multimeter?

 

[TL2021]

Is the inverter cutting off because of the 33V spike? many cut off at 32V or less.

27.6V is at a high state of charge.

Check all connections - everything is tight and secure.

Have you confirmed any readings with a multimeter?

The inverter cuts off because the battery cuts off. The voltmeter drops rapidly when the inverter starts pulling from the battery. I saw it drop from 27v to 24v before the battery cut off. I’m assuming the BMS cut it off.

Everything is tight and secure

I have confirmed the readings with a multimeter. Sometimes the reading differs from the battery and the BMS connection.

 

[MisterSandals]

I hooked up my car to the inverter.

How big is the inverter and what kind of load is your car pulling?

I don't think a battery BMS would cut out at 24v, more likely something like 20v, possibly 21v but having the battery info (assuming internal BMS?) or BMS info would help resolve this.

 

[TL2021]

Is this connected to the battery or the SCC's load output?

Have you tested any of the volt readings with an actual digital volt meter or are these readings from the various devices displays?

Does the inverter cut off with an error code like low voltage or ??
Why do you suspect that the controller and charger think the battery is full?
Are you simultaneously using the MPPT SCC and the Victron 24v charger?

Sorry, there is a LOT going on in your description, just trying to figure it out.

Idk how to answer that so I attached a pic lol. Both I think?

yes

The inverter cuts off because the battery cuts off

The battery and controller stop pushing amps when the voltage reads 29.2 so I assumed it was reading battery as full

No

 

[TL2021]

How big is the inverter and what kind of load is your car pulling?

I don't think a battery BMS would cut out at 24v, more likely something like 20v, possibly 21v but having the battery info (assuming internal BMS?) or BMS info would help resolve this.

4000w/8000w. The car pulls between 2000-2100 watts.

 

[pollenface]

I suspect the inverter is at fault, it should run fine at 26v.

 

[TL2021]

I’ll also add that when the battery cuts off, I usually have to plug in the battery charger for it come back on. Idk why

 

[MisterSandals]

I’ll also add that when the battery cuts off, I usually have to plug in the battery charger for it come back on. Idk why

4000w/8000w. The car pulls between 2000-2100 watts.

2000w / 24v = 83A so 200A BMS should be ok for current.
Do you have a clamp meter with a surge/inrush current counter?

What BMS? Any custom settings or do you know the BMS cutoff values?

 

[snoobler]

With the inverter pulling the load in question, record these 3 voltages:

1) voltage AT the charge controller terminals.
2) voltage at the battery terminals.
3) voltage across any fuse or resistor. This means you place the probes on the bolts/screws attaching the fuse/breaker to the wires.

Questions:
A) Did you procure these cells from a known reputable source?
B) Did you top balance the pack?
C) Did you confirm the battery capacity?
D) How much solar do you have?
E) What are you charging?

 

[Forbisher]

What is happening?

8s 280ah
8s 200a bms
60a mppt solar charge controller
Victron Blue Smart 24v charger

You bought a Victron but got a knock off PowMr SCC.

 

[TL2021]

2000w / 24v = 83A so 200A BMS should be ok for current.
Do you have a clamp meter with a surge/inrush current counter?

What BMS? Any custom settings or do you know the BMS cutoff values?

I do not have one with a surge counter

This is the BMS. No custom setting.Daly BMS

 

[TL2021]

You bought a Victron but got a knock off PowMr SCC.

Couldn’t find a knock off charger that does what the victron does ??‍

 

[TL2021]

With the inverter pulling the load in question, record these 3 voltages:

1) voltage AT the charge controller terminals.
2) voltage at the battery terminals.
3) voltage across any fuse or resistor. This means you place the probes on the bolts/screws attaching the fuse/breaker to the wires.

Questions:
A) Did you procure these cells from a known reputable source?
B) Did you top balance the pack?
C) Did you confirm the battery capacity?
D) How much solar do you have?
E) What are you charging?

I’ll try to get those measurements when I find a load small enough that won’t make the battery cut off. Currently it won’t stay on long enough to do it with charging my car.

A. Some reseller on Aliexpress. They seem legit
B. Yes
C. Yes
D. 4 x 250 watt panels. Two series in parallel.
E. Im either charging my batteries or my car. Ford Fusion Energi.

 

[snoobler]

"Worked fine for a day." Missed that. You likely don't have enough solar and depleted your battery. You continue to have it at a low state of charge, and thus it's performing poorly.

FFHE has a 7.6Kwh Battery, which is a little more than your LFP bank. I'm using 8 of them to build a large off-grid battery. If you're using this to charge your battery from full to empty daily, you don't have anywhere near enough solar unless you're on a 2-axis tracking mount with clear skies every day.

On a great summer day, your panels can produce about 5kWh. In winter, maybe half that unless you're tilting them steeply to the South. That assumes your cheap MPPT is performing optimally.

For the voltage check, it needs to be a big enough load to cause a meaningful voltage drop.

What battery monitor are you using?

 

[TL2021]

"Worked fine for a day." Missed that. You likely don't have enough solar and depleted your battery. You continue to have it at a low state of charge, and thus it's performing poorly.

FFHE has a 7.6Kwh Battery, which is a little more than your LFP bank. I'm using 8 of them to build a large off-grid battery. If you're using this to charge your battery from full to empty daily, you don't have anywhere near enough solar unless you're on a 2-axis tracking mount with clear skies every day.

On a great summer day, your panels can produce about 5kWh. In winter, maybe half that unless you're tilting them steeply to the South. That assumes your cheap MPPT is performing optimally.

For the voltage check, it needs to be a big enough load to cause a meaningful voltage drop.

What battery monitor are you using?

I waited until my battery was “full” to try to charge my car again. However, it would never charge past 27.6v. I tried both my SCC and battery charger separately to charge it past 27.6, but they both read that the battery as 29.2 or greater when I turn them on.

Im in the process of tearing everything down to get to the cells. I’m hoping I don’t have a bad BMS or battery cell.

I have a Drok 7-1 voltmeter.

 

[pollenface]

Is your charge controller set up for 8s Lifepo4?

 

[TL2021]

Is your charge controller set up for 8s Lifepo4?

It supports it. You set the parameters as if it’s a 12v pack and the SCC detects if it’s 12v, 24v, or 48v.

So after tearing everything down, accidentally touching the main positive lead to the main negative causing a small fire, and striping yet another thread in a cell, I quit troubleshooting. ? I’m hurting more than helping.

However, rebuilding might have helped it. The SCC is pushing 35 amps this sunny morning, and the voltage reading from the battery isn’t jumping up wildly. So maybe something came loose after Day 1 ??‍.